The emerging field of regenerative medicine will require a reliable source of stem cells in addition to biomaterial scaffolds and cytokine growth factors. Adipose tissue represents an abundant and accessible source of adult stem cells with the ability to differentiate along multiple lineage pathways. The isolation, characterization, and preclinical and clinical application of adipose-derived stem cells (ASCs) are reviewed in this article.

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Adipose-Derived Stem Cells for Regenerative Medicine

Compared with bone marrow-derived mesenchymal stem cells, adipose tissue-derived stromal cells (ADSC) do have an equal potential to differentiate into cells and tissues of mesodermal origin, such as adipocytes, cartilage, bone, and skeletal muscle. However, the easy and repeatable access to subcutaneous adipose tissue and the simple isolation procedures provide a clear advantage. Since extensive reviews focusing exclusively on ADSC are rare, it is the aim of this review to describe the preparation and isolation procedures for ADSC, to summarize the molecular characterization of ADSC, to describe the differentiation capacity of ADSC, and to discuss the mechanisms and future role of ADSC in cell therapy and tissue engineering. An initial effort has also been made to differentiate ADSC into hepatocytes, endocrine pancreatic cells, neurons, cardiomyocytes, hepatocytes, and endothelial/vascular cells. Whereas the lineage-specific differentiation into cells of mesodermal origin is well understood on a molecular basis, the molecular key events and transcription factors that initially allocate the ADSC to a lineage-specific differentiation are almost completely unknown. Decoding these molecular mechanisms is a prerequisite for developing novel cell therapies.

https://stemcellsjournals.onlinelibrary.wiley.com/doi/epdf/10.1634/stemcells.2006-0589

Concise review: adipose tissue-derived stromal cells--basic and clinical implications for novel cell-based therapies.

Recent advances in understanding the cellular and molecular signaling pathways and global transcriptional regulators of adult mesenchymal stem cells have provided new insights into their biology and potential clinical applications, particularly for tissue repair and regeneration. This review focuses on these advances, specifically in the context of self-renewal and regulation of lineage-specific differentiation of mesenchymal stem cells. In addition we review recent research on the concept of stem cell niche, and its relevance to adult mesenchymal stem cells.

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Mesenchymal stromal cells. Biology of adult mesenchymal stem cells: regulation of niche, self-renewal and differentiation

http://basicmed.med.ncku.edu.tw/public/project/1159-1334224338-1.pdf

Bone marrow-derived myofibroblasts contribute to the mesenchymal stem cell niche and promote tumor growth.

Objective To evaluate the feasibility, safety, and immunological effects of intrathecal and intravenous administration of autologous mesenchymal stem cells (MSCs) (also called mesenchymal stromal cells ) in patients with multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS). Design A phase 1/2 open-safety clinical trial. Patients Fifteen patients with MS (mean [SD] Expanded Disability Status Scale [EDSS] score, 6.7 [1.0]) and 19 with ALS (mean [SD] Amyotrophic Lateral Sclerosis Functional Rating Scale [ALSFRS] score, 20.8 [8.0]) were enrolled. Intervention After culture, a mean (SD) of 63.2 × 10 6 (2.5 × 10 6 ) MSCs was injected intrathecally (n = 34) and intravenously (n = 14). In 9 cases, MSCs were magnetically labeled with the superparamagnetic iron oxide ferumoxides (Feridex). Main Outcome Measures The main outcome measure was the recording of side effects. Follow-up (≤25 months) included adverse events evaluation, neurological disability assessment by means of the EDSS, magnetic resonance imaging to exclude unexpected pathologies and track the labeled stem cells, and immunological tests to assess the short-term immunomodulatory effects of MSC transplantation. Results Twenty-one patients had injection-related adverse effects consisting of transient fever, and 15 reported headache. No major adverse effects were reported during follow-up. The mean ALSFRS score remained stable during the first 6 months of observation, whereas the mean (SD) EDSS score improved from 6.7 (1.0) to 5.9 (1.6). Magnetic resonance imaging visualized the MSCs in the occipital horns of the ventricles, indicating the possible migration of ferumoxides-labeled cells in the meninges, subarachnoid space, and spinal cord. Immunological analysis revealed an increase in the proportion of CD4 + CD25 + regulatory T cells, a decrease in the proliferative responses of lymphocytes, and the expression of CD40 + , CD83 + , CD86 + , and HLA-DR on myeloid dendritic cells at 24 hours after MSC transplantation. Conclusion Transplantation of MSCs in patients with MS and ALS is a clinically feasible and relatively safe procedure and induces immediate immunomodulatory effects. Trial Registration clinicaltrials.gov Identifier:NCT00781872

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Safety and immunological effects of mesenchymal stem cell transplantation in patients with multiple sclerosis and amyotrophic lateral sclerosis.

The biologic characteristics of mesenchymal stem cells (MSCs) isolated from two distinct tissues, bone marrow and adipose tissue were evaluated in these studies. MSCs derived from human and non-human primate (rhesus monkey) tissue sources were compared. The data indicate that MSCs isolated from rhesus bone marrow (rBMSCs) and human adipose tissue (hASCs) had more similar biologic properties than MSCs of rhesus adipose tissue (rASCs) and human bone marrow MSCs (hBMSCs). Analyses of in vitro growth kinetics revealed shorter doubling time for rBMSCs and hASCs. rBMSCs and hASCs underwent significantly more population doublings than the other MSCs. MSCs from all sources showed a marked decrease in telomerase activity over extended culture; however, they maintained their mean telomere length. All of the MSCs expressed embryonic stem cell markers, Oct-4, Rex-1, and Sox-2 for at least 10 passages. Early populations of MSCs types showed similar multilineage differentiation capability. However, only the rBMSCs and hASCs retain greater differentiation efficiency at higher passages. Overall in vitro characterization of MSCs from these two species and tissue sources revealed a high level of common biologic properties. However, the results demonstrate clear biologic distinctions, as well.

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Biologic properties of mesenchymal stem cells derived from bone marrow and adipose tissue

Low oxygen tension is thought to be an integral component of the human mesenchymal stem cell (hMSC) native bone marrow microenvironment. HMSC were cultured under physiologically relevant oxygen environments (2% O2) in three-dimensional (3D) constructs for up to 1 month in order to investigate the combined effects of chronic hypoxia and 3D architecture on hMSC tissue-development patterns. Hypoxic hMSC exhibited an extended lag phase in order to acclimatize to culture conditions. However, they subsequently proliferated continuously throughout the culture period, while maintaining significantly higher colony-forming unit capabilities and expressing higher levels of stem cell genes than hMSC cultured at 20% O2 (normoxic) conditions. Upon induction, hypoxic hMSC also expressed higher levels of osteoblastic and adipocytic differentiation markers than normoxic controls. Hypoxia induced increased total protein levels in hMSC throughout the culture period, as well as significantly different fibronectin expression patterns suggesting that oxygen levels can significantly affect tissue-development patterns. Importantly, hMSC maintained the ability to thrive in prolonged hypoxic conditions suggesting that hypoxia may be an essential element of the in vivo hMSC niche. Further studies are required to determine how variations in cellular characteristics and ECM expression impact on the physiological properties of the engineered tissue, yet these results strongly indicate that oxygen tension is a key parameter that influences the in vitro characteristics of hMSC and their development into tissues.

Effects of hypoxia on human mesenchymal stem cell expansion and plasticity in 3D constructs

Mesenchymal stem cells (MSC) derived from bone marrow stem cells (BMSC) and adipose tissue stem cells (ASC) of humans and rhesus macaques were evaluated for their cell cycle properties during protracted culture in vitro. Human ASCs (hASC) and rhesus BMSCs (rBMSC) underwent significantly more total population doublings than human BMSCs (hBMSC) and rhesus ASCs (rASC). The cell cycle profile of all MSCs was altered as cultures aged. hMSCs underwent an increase in the frequency of cells in the S phase at P20 and P30. However, rhesus MSCs from both sources developed a distinct polyploid population of cells at P20, which progressed to aneuploidy by P30. Karyotype analysis of MSCs revealed the development of tetraploid or aneuploid karyotypes in the rhesus cells at P20 or P30. Analysis of the transcriptome of the MSCs from early and late passages revealed significant alterations in the patterns of gene expression (8.8% of the genes were differentially expressed in hBMSCs versus hASCs, and 5.5% in rBMSCs versus rASCs). Gene expression changes were much less evident within the same cell type as aging occurred (0.7% in hMSCs and 0.9% in rMSC). Gene ontology analysis showed that functions involved in protein catabolism and regulation of pol II transcription were overrepresented in rASCs, whereas the regulation of I kappa B/nuclear factor-kappaB cascade were overrepresented in hBMSCs. Functional analysis of genes that were differentially expressed in rASCs and hBMSCs revealed that pathways involved in cell cycle, cell cycle checkpoints, protein-ubiquitination, and apoptosis were altered.

https://cancerres.aacrjournals.org/content/canres/68/11/4229.full.pdf

Long-term in vitro expansion alters the biology of adult mesenchymal stem cells.

Aging alters tissue resident mesenchymal stem cell properties.

Mesenchymal stem cells (MSCs) have been isolated based on the ability of adherence to plastic surfaces. The potential of these cells to differentiate along multiple lineages is the key to identifying stem cell populations in the absence of molecular markers. Here we describe a homogenous population of MSCs from mouse bone marrow isolated using a relatively straightforward and novel approach. This method is based on the combination of frequent medium change (FMC) and treatment of the primary cultures with trypsin. Cells isolated using this method demonstrated the MSCs characteristics including their ability to differentiate into mesenchymal lineages. MSCs retained the differentiation potentials in expanded cultures up to 10 passages. Isolated MSCs were reactive to the CD44, Sca-1, and CD90 cell surface markers. MSCs were negative for the hematopoietic surface markers such as CD34, CD11b, CD45, CD31, CD106, CD117 and CD135. The data presented in this report indicated that this method can result in efficient isolation of homogenous populations of MSCs from mouse bone marrow.

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Reza Izadpanah

Papers

Biologic properties of mesenchymal stem cells derived from bone marrow and adipose tissue

Effects of hypoxia on human mesenchymal stem cell expansion and plasticity in 3D constructs

Long-term in vitro expansion alters the biology of adult mesenchymal stem cells.

Aging alters tissue resident mesenchymal stem cell properties.

An efficient method for isolation of murine bone marrow mesenchymal stem cells.